Addition of a desiccant to a fluidized iron reduction process



Patented Apr; 24, 1951 M ,z ssosoa T i pp'ITioN-or: A-nEsIcANrTOIA'FLUIDIIZED' I RQN REDUCTION i wimamfL-I h staam ra al--toThe.f1exas Company, New York,vN. Y.,

ere "spews No Drawing.

The present. invention. relates, to catalystsfor the synthesis of.hydrocarbons, oxygenated hydro carbons and the like, from carbon oiiideand hydrogen, and is more particularly concernedwiththe-step ofcatalystreduction.

-In accordance with this inventioman oxidized metal of the iron group,such. for examp1e,'-as' ferric oxide or the like, usually associatedwith: suitable promoters, activators, or :other modify;-

ing agents, isw-reduced atelevated temperatures and preferably undersuperatmospheric pressure "i -by='contact with a stream of hydrogen.-:Reduc'--- tion is carried out ,in the presence of.a ndI 1- gaseousdesiccant material eilective totake up water promptly as it is.producedin-the course of reduction and thus enablee lthereduction, -to

.firocdinthe absence oi or-in thepresence of; a

substantially lower partial pressure of water var than that whichprevails the absencejof -,the'desiccant.

:T Advantageously; use of the desiccant material a isp'ostponed ujnti-llater stages of. reduction, when- ;the' reaction between'the.hydrogen-and the"re;-

f -nrainingoxide becomes excessively slow and dif:-'

ficult; At this time. presence oi the. desiccant material in thereduction zone appears to speed rect productionof'de hydrocarbons and.oxygenated hydrocarbons.

'P'referably, however, such use ofthe catalyst is preceded by a'con'ditiqning'treatment,such as is disclosed. in cofiendingXapplicationSerial No.

570,223, filed December 28, 1944, now-UL S. 2,445,795, whereinuse isinitiated at. a temper-- ature substantially below normal operatingtein- I temperatures 0 and iacilitate'materially the sluggish reaction,-

favor rapid completion of the reaction.

-I 'rovis'1on may be made for continuously intro? 'ducing a solidParticle, desiccant material to the-- reduction zone ass, finelydivided. phaseisuspended 11in theflow 01' hydrogen;Asthe'hydrogen'stream-j -I- circulates cyclically through the.reducingzohe, ---th isuspended particles, absorb water Vapor and;

f 1 3 pass out with thenresidual hydrogen withdrawn from the zone.-Alternatively;=a sufiicient batch of relatively coarser, particledesiccant may be 1 retained in intimate admixture with ,the catalystcompletion of the. reduction step, where- .upon pneumaticseparationmaybe effected by inthe how. or reduction gas so that the hydrateddesiccant isblown out of the. zone. "Ob.--

viously, in view of the foregoin' any other suitjablemethod orseparation ,be employed I The catalyst,- reduced as above, is in 'a termeffective tor contact "with-synthesis gas; comprising hydrogen andcarbon monoxide, under-reac tion conditions, including anelevatpdtemperatureand pressure at which the-hydrogen catalr nm duc s h x b n moi ew i .5 2

. .substantially increasing the ratejoi catalyst re-. --duction andresulting in .a more completely reduced product; Presumably, this efiect'follows 5 :troni=the fact thatwater vapor tends to suppress Areduction, while lower. water vapor concentrations inthe upflow ofgases.

prature--with a slow increase to opera'tingtem- 'perature verasubstantialtiime period;

From the foregoing it will'be apparent that an v essentialcharacteristic of the present desiccant material "ordehy'drating'agentis that it readily I combines. with water atthe eleyated'temper- I ature and pressure at which-reductions efi ected;

to form a compound or compounds stable under" such conditions. Infshort, the-dissociation pres ,s'ure of thecompound iormed bycombination .of

the desiccantlwithiwater-is lower; at-the temperature prevailing in thereduction zone,'than the'partial pressure of water vapor which would.

prevail iii-ordinary operation, preferably less than that partialpressure 0')? water vapor in-the gases after condensation, at pressuresin the'order of 100.120 40c, pounds per square inch', and at normalAnother-= esirabl e .feature 5": the. dehydrating into smaller; fiufiyparticle'swhicli can be many :ing steps or'can be sweptput by ashghtincrease Examples of efiective d aegfit; materials are carbides-ofaluminum and par'ticularlyalkaline earth metals, such; for example, ascalcium car bideand barium carbide, which combine chemically .withwatenyaporlto for-1n corre ponding 4 meme metal oxides. and liberategaseous acctylene." The carbides of the rare earth metalsjare alsouseful inthis respect. Onthe other handrmetal hydrides, such forexample, as calcium or barium hydride, are similarly efiectivetdcombine' with watervapor; simultaneously liberating additionaihydrogen to'supplement the stream of re-- ducing agent. It'i's to benoted thatsubstances such asicalcium' oxide, barium oxide andmagnesiumoxide.- which chemically-combine with water. to form thehydroxides and substances such as calcium sulfate and" the perchlorates.of magnesium'and barium which form hydrates, are

also useful as desiccants' in the present process,- v

agnts'wmchremov water by chemicalcom bination are, in general, moresuitable for use in ired products, includin f about l fandpreierablyfagent is that, during "the fcourse pihydration, it"

advar'itag eo'usly tends to disintegrate or crumble "removed from thecataly'st'by ordinary'separat fusible hydrogen, -This follows reducinggas.

Iii-either case, introduction of desiccant par reduction steps carriedout at relatively high temperatures, as for example, in the range ofabout 600 to 800 E, as contrasted with-those which form, hydrates, whichare usually effective at lower;-

temperatures, for'example, below 'about 400 F. That is to say, compoundsthat are formed by chemical interaction oithe water and desiccant aremore stable since they require higher temperatures to convert; themtoftheir anhydrides.

The reduction of the catalyst contemplated in accordance with thepresent invention, may be carried outat the lower temperature ranges;but, is preferably efiected in the-case of a catalyst comprising iron,at temperatures ranging-above about 600 F.,'as' for example, 650 to 700R,

' frequently under more elevatedtemperatures up to 1000" F. and above,usually under 'superatmo'spheric pressure, ranging, for example, up to200 j to 400 pounds per square inch and normally is' accompanied byformation of substantial amounts of water.

As-the reduction approaches completion, thereaction slows considerablyin thefpresence of ingly, evenwhere the hydrogen, is continuously passedthrough the reduction zone, withdrawn, dried and recirculated, atsubstantial-rates, completion of the-reduction requires excessive timewhichthey are entrained in and removed in circulating flow of reducinggas. Alternatively, a stoichiometric quantity ofseparate provision for'mixing'and distributing the desiccant in the catalyst powder isobviated.

As intimated above, the rateof gaseous flow through the fluidp'hasecatalyst mass, and de-' gree of subdivision of the desiccant powder maybe regulated so that the catalyst particles remain within. the reductionzone while the desiccant is withdrawnwith the efiiuenthydrogen. Thiscanbe effected with the catalyst in either dense'fiuid phase, or fixed bedcondition' 011, I

desiccant may be mechanically mixed with the catalyst and the reductioncompleted under flow rates at which entrainment of solid particles isnegligible, and-thereafter, the flow rate in-' creased to a value atwhich the morebuoyant desiccantpart'icles are effect blown out of onlysmall proportionsof water-vapor. Accordthe catalyst,

Provision may be made for filtering, electrostatically separating orotherwise removing particles from theefliuent hydrogen. Similarly, any

and results inan uneconomical loss ,of highly dif- ,from the fact thatdry. hydrogen introduced to the zone is promptly contaminated withproductwa'ter van m 4, o. Therefore, the present invention effects asubstantial increasein'rate of reduction by the removal -of water vaporas it'is formed so that the partial pressure of water vapor issubstantially lowered in; the reduction zone. Thus. the decrease wardthe end 'of the operation is overcome. Thispermits reduction at lowertemperatures and at conventionalmeans of separation may be employed torecoverdesiccant solid from the treated" catalyst. For example, magneticseparation affords an effective means whereby the finalreduced catalystis preferably rendered substantiall-yfre from the added-solid'desiccant,

In accordance with one method of operation,

a 'stream of ,hydrog'en is continuously passed througha mass of ironoxide powder, comprising mainly F6304 and Feat): finer than about meshand containing a more or less uniform distribue in the-reduction ratenormally encouriterd-totion of particles down-to about 20 microns indiameter,

, upwardly through the-mass at. a temperature of lower rates of hydrogencirculation of the reduca ing gas than hithertofore.Therefora'ztheprepa'ration ofsubstantial quantities of catalystmay beeffected with a more economical utilization of hydrogen and lessloss'oi't mfi, nd the final product may be more fully and completely reduced. In particular, the saving'in-hydrogen lost'by 'difiusion duringmore, extended treatment;

- may involve a substantial economy in operation. .1 A-s intimatedabove, it ing the desiccant in solid particle form, prefer .ably in theform of powder or within the same or similar particle-sizerange' as thecatalyst par is contemplated employ-I ticles so that intimate contact'iseffected within the reaction zone.

The catalyst powder is usually in the form of a mass of solid particlesdisposed loosely within the zone and preferably aerated to a "densefluid phaseuby means of the upflowing reducing gas. The invention,however, is not thuslimited, and

broadly contemplates the reduction of a'nysuitable synthesis catalyst,whether in the form of fluid-or stationary bedoffixed particles. In thefixed bed type of operation, or even with so-called moving" bedsof'catalyst, the'particles may be in relatively coarse forin,,providingsubstantial internal free space through which a finely powdereddesiccant will-flow when suspended in the ticles as a suspended phaseentrained inthe reducing gas results in immediate distribution andintermixture of the desiccant with the mass of catalyst particles;Operating in this manner,

about 700 F. and at, a. suitable linear velocity such that the catalystparticles'are held in a dense fluid phase, without. material entrainmentin the eilluent gas. Unconsumed excess hydrogen is withdrawn from thetop ofHthedense fluid" phase,-cooled to condense contained moistureandjseparated from the condensed water. Thereafter, it is usuallycontinuously reheated, and

continuously recycled to the inlet with an ap propriatesupplement tain.the required no Under these conditions, reduction of the catalys'tproceeds at a fairly rapid rate until somewhat'aboveabout 80, per centoithe oxide has :been reduced to metallic-iron.

At this point-"a batch of powderedcalcium carbide isthoroughly mixedwith the" catalyst.

" V in at least the stolch-iometrical proportion, efiecduring subsequentreduction.

tive under thetemperature and pressure condi-' tions prevailing toabsorb the-water vapor formed Recirculation of V the hydrogen iscontinued as before, until at least and preferablyIlDOp'er centofthecatalyst has been completely reduced, and the desiccant -'is thenseparated D from the catalyst by any de-- sired means.- I I In'accordance with one specific embodiment of the present invention, thereis provided about I50 pounds of an alkali impregnated ferric oxide finerthan tie-mesh, about 80 per cent being finer than mesh, and about 30 percent being finer than 325 mesh.

. The ferric oxide contains approximately 2 per cent alumina and about 1per cent. potassium,

Preferably, the hydrogenis passed of fresh hydrogen to main the raactionzone: and the solid panic. material-1s in the form-oi.agrelafii-vely'fineimwd r i. The mmn a acmrding m claim 'wbereiz heoxidation prpduqtis in arrelaitlvely marge.

Particle form @1101; that it rgmaimre semiau which remains suspended in.the tmam 91mm 10 2,252,712 en and i s contin l w th awn fr m the m?duqtion'zopg m-exitxamment in. the atflpeni; gas-

1. IN THE PREPARATION OF CATALYSTS FOR THE SYNTHESIS OF HYDROCARBONS,OXYGENATED HYDROCARBONS AND THE LIKE BY THE CATALYTIC REDUCTION OFCARBON MONOXIDE WITH HYDROGEN WHEREIN AN OXIDATION PRODUCT OF A METAL OFTHE IRON GROUP IS REDUCED BY A STEAM OF HYDROGEN THE IMPROVEMENT WHICHCOMPRISES PASSING SAID STREAM OF HYDROGEN IN CONTACT WITH A POWDEREDMASS OF SAID OXIDATION PRODUCT IN A REDUCTION ZONE UNDER REACTIONCONDITIONS INCLUDING AN ELEVATED TEMPERATURE AT WHICH THE METAL COMPOUNDPASSAGE OF HYDROGEN METALLIC STATE, CONTINUING PASSAGE OF HYDROGEN UNTILAT LEAST ABOUT 80 PERCENT OF THE POWDER IS REDUCED TO THE METALLIC FORM,THEREAFTER ADDING A SOLID PARTICLE DESICCANT MATERIAL EFFECTIVE TOCOMBINE WITH WATER VAPOR UNDER SAID REACTION CONDITIONS WITH THEFORMATION OF A DRY SOLID PRODUCT INEFFECTIVE TO IMPAIR REDUCTION OF THEMETAL AND CAPABLE OF BEING SEPARATED FROM THE CATALYST PARTICLES,CONTINUING SAID PASSAGE OF HYDROGEN UNDER SAID REACTION CONDITIONS UNTILREDUCTION IS SUBSTANTIALLY COMPLETED AND SEPARATING THE RESULTINGDESICCANT MATERIAL FROM SAID REDUCED CATALYST.